ENHANCED DIAGNOSTIC EPR AND ENDOR SPECTROSCOPY OF RADICAL SPIN ADDUCTS OF DEUTERATED ALPHA-PHENYL N-TERT-BUTYL NITRONE

Deuterated analogues of C-phenyl N-tert-butyl nitrone (PBN) were synth esized to provide significant gains in spectral sensitivity and resolu tion in electron paramagnetic resonance (EPR) and electron nuclear dou ble resonance (ENDOR) applications. Three deuterated alpha-phenyl N-te rt-butyl nitrones (PBNs) were prepared. EPR spectra of the correspondi ng radical spin adducts with the phenyl ring (PBN-d5-R.) or tert-butyl moiety (PBN-d9-R.) deuterated were found to enhance disclosure of the structure of the added radical. The most dramatic increases in EPR re solution, however, were not realized until both the phenyl and tert-bu tyl groups were deuterated (PBN-d14-R.). Here, baseline resolution of unique long-range (eg. gamma- and delta-) hyperfine splittings from th e radical addend could be displayed. Representative radical spin adduc ts of PBN-d14 (methyl, hydroxyl, aminyl, cyanyl, carbamoyl, and vinyl) were prepared and compared with those of PBN to, illustrate this poin t. It is also shown that when even higher spin adduct resolution is de sired the combination of spin trap deuteration and ENDOR may be applie d to advantage.